Electrostatic spray coating apparatuses are typically supplied with a fluid which is electrically charged either before or after atomization, then applied to an electrically grounded workpart.
In non-electostatic coating applications, coating materials composed of a mixture of two components have been found to provide superior results. The two component coating materials, typically, comprise a paint component and a hardener component which are thoroughly mixed together at a predetermined optimum ratio to provide a fast-drying, hard material.
There are generally two reasons why two component coating materials are considered nonadaptable to the electrostatic spray coating art. The first is that, because two component materials harden very fast when mixed at the proper proportions, they cannot be mixed together until just prior to application. Therefore, the mixing must take place within the spray booth at a location proximately upstream of the applicator. This requirement leads to the second, and more basic, reason why two component systems are rare in the electrostatic spray coating art. Namely, the two components must be mixed together at very precise proportions in order to achieve their advantageous results over single component materials. Even minute variations from the optimum mixing ratios can result in serious coating flaws, e.g., inability to harden, cracking, peeling, etc.
The prior art Behr Industrieanlaegen "Audi 001" spray coating apparatus mixes two paint components prior to application. This system employs two 5-phase 60 volt DC stepper motors to drive separate gear pumps through a 3:1 gearbox. Proximity sensors are used to sense motor speed.